Interpretation ID: nht94-7.21

DATE: March 25, 1994

FROM: John Womack -- Acting Chief Counsel, NHTSA

TO: Thomas D. Turner -- Manager, Engineering Services, Blue Bird Body Company

TITLE: None

ATTACHMT: Attached to letter dated 11/15/93 from Thomas D. Turner to John Womack

TEXT:

This responds to your letter of November 15, 1993, in which you requested an interpretation of the final rule issued by this agency on January 15, 1993, 58 FR 4586, which amended Federal Motor Vehicle Safety Standard (FMVSS) No. 222, School Bus Passenger Seating and Crash Protection to include requirements for wheelchair securement devices and occupant restraint systems.

You referred to the second sentence in S5.4.3.2 of the standard which provides in pertinent part: "When more than one wheelchair occupant restraint shares a common anchorage, the anchorage shall be capable of withstanding a force of 13,344 Newtons multiplied by the number of occupant restraints sharing that anchorage." You stated that you believe that this language is intended to address the situation where restraints from two different wheelchair occupant restraint systems share a common anchorage, and is not intended to address the situation "where the lower end of an upper torso restraint joins the pelvic restraint and goes to one of the rear floor anchorages of a single occupant's restraint system." You stated that if the latter, the floor anchorage would be required to withstand a force of 13,344 Newtons each for the upper torso restraint and the pelvic restraint; and if the wheelchair was also secured to that floor anchorage, the anchorage would be required to withstand 3 x 13,344 Newtons.

Your letter included two figures illustrating typical wheelchair securement and occupant restraint system designs. In Figure 1, the upper torso restraint is attached to the lap belt at the buckle, and the lap belt is attached to the vehicle at the same anchorage as the rear anchorage for the wheelchair securement device. In Figure 2, the upper torso restraint is also attached to the lap belt; however, the lap belt is attached to the rear wheelchair securement device instead of the wheelchair securement anchorage. You asked for verification that the required load for the rear anchorages for both designs is 2 x 13,344 Newtons rather than 3 x 13,344 Newtons.

You are correct that the load for the rear anchorages for both these designs would be 26,688 Newtons (2 x 13,344 Newtons). The relevant section to determine this load is S5.4.3.2(e) which states:

When a wheelchair securement device and an occupant restraint share a common anchorage, including occupant restraint designs that attach the occupant restraint to the securement device or the wheelchair, the loads specified by S5.4.1.3 (13,344 Newtons) and S5.4.3.2 (13,344 Newtons) shall be applied simultaneously...

The term "wheelchair occupant restraint" includes both the pelvic and upper torso restraints (see S5.4.4). In your designs, each rear floor anchorage would be required by S5.4.3.2(e) to withstand a combined force of 26,688 Newtons, which includes the load specified for the wheelchair occupant restraint and the load specified for the wheelchair securement device.

The second sentence of S5.4.3.2, which you quoted in your letter, addresses the situation where the wheelchair occupant restraints for more than one wheelchair, e.g. two wheelchairs, are secured to the same floor anchorage. This requirement parallels a requirement in S5.4.1.3 which addresses the situation where the wheelchair securement devices for more than one wheelchair are secured to the same floor anchorage. Thus, for example, if either of your designs were installed in a bus such that the right rear anchorage was shared with another identical wheelchair securement and occupant restraint system (functioning as the left rear anchorage for the second system), that floor anchorage must be capable of withstanding a force of 13,344 Newtons for each occupant restraint system and 13,344 Newtons for each wheelchair securement system, for a total force of 4 x 13,344 Newtons, such force to be applied simultaneously as required by S5.4.3.2(e).

I hope you find this information helpful. If you have any other questions, please contact Walter Myers of my staff at this address or by phone at (202) 366-2992.